This proposal is designed to continue studies to determine with more precision and accuracy, the storage and binding sites of the gonadotropins: follicle stimulating hormone (FSH), luteinizing hormone (LH), adrenocorticotropin (ACTH), gonadotropin releasing hormone (GnRH) and estradiol in the adenohypophysis of rats with ultrastructural immunocytochemical techniques. Several experimental models will be studied to elucidate the functional significance of previous findings. These include: 1. changes in gonadotroph morphology with enhanced secretory activity; 2. the existence of intracellular (granular) GnRH; 3. the presence of FSH and LH in the same granule; 4. the existence of a cell containing ACTH and FSH. In vivo models include a study of rats in puberty in the estrous cycle and after castration and adrenalectomy. In vitro experiments include test designed to determine if gonadotropes in culture synthesize or sequester GnRH and the effect of exogenous GnRH on endogenous stores. Portal perfusion studies are designed to determine the effect of GnRH on changes in cell morphology and the extent to which microtubules and microfilaments are involved in these changes. For all experimental groups, cell secretion of the hormones in question will be monitored by radioimmunoassay.